Much is known concerning the immunobiology of antigen recognition by T lymphocytes. For example, the T cell receptor for antigen has been defined genetically, the association of this receptor with the CD3 complex of proteins has been established, and the accessory functions of the CD4 and CD8 proteins in stabilizing the recognition of antigen presented in association with either Class II or Class I MHC proteins has been demonstrated. What has not been established is what mechanisms are involved in T lymphocyte localization into sites of inflammation and antigen deposition, thereby allowing antigen-specific T cells to carry out their effector functions in vivo. The proposed studies are base don the central hypothesis that endothelial modification must occur at sites of inflammation to facilitate the extravasation of blood borne T lymphocytes into the tissues. Further, endothelial differentiation in inflammatory tissues would be regulated by cytokines produced by antigen-stimulated T cells. In these studies, polyurethane sponges will sere as a matrix for antigen deposition, endothelial differentiation, and lymphocytic infiltration. Specifically, we will: 1) demonstrate phenotypic changes in vascular endothelia associated with T cell entry into inflammatory tissues. We will use immunohistochemistry and mAb to identify alterations of the vascular endothelia in antigen-containing sponges. 2) identify receptor- ligand interactions which mediate T cell adhesion to inflammatory endothelia. mAb specific for differentiated endothelia and T cell surface proteins will be incorporated into ex vivo adhesion assays and in vivo lymphocyte homing assays to block lymphocyte adhesion and extravasation. 3) evaluate cytokine regulation of inflammatory endothelial differentiation. Cytokines with known activity on endothelial cell behavior in vitro will be assessed for a similar activity in vivo. 4) evaluate T cell subset participation in inflammatory endothelial differentiation. T cell subsets will be depleted in vivo to test the hypothesis that subsets of T cells regulate endothelial differentiation. 5) determine if immunosuppressive drugs which interfere with T cell accumulation at sites of antigen deposition do so by interfering with the development of inflammatory endothelia. These studies will provide a comprehensive analysis of T lymphocyte-inflammatory endothelia interactions which result in lymphocyte extravasation in vivo. In understanding the regulation of this process, future experimentation will be directed at pharmacologic manipulation of disease states characterized by lymphocytic infiltration into inflammatory tissues.